As is well known and understood, sheet-metal hole saws are oftentimes used to drill into such cavities and enclosures as electric control boxes, by technicians working in the field. Similarly, such hole saws are oftentimes used by air-conditioning repair workers drilling about a compressor, in areas adjacent the coolant coil, or where electrical contacts are present.
As is well known in these and other uses, the operation with a hole-saw is typically "one-handed"--which creates a problem if an unequal pressure is applied in utilizing the saw in making its cut. For example, it is not unusual to find that one side of the hole saw goes in faster, or easier than the other, causing the drill to twist around, oftentimes ripping the sheet metal, or tearing the cutting teeth. On other occasions, even if the binding of the teeth that results is not sufficient to damage the sheet metal or the bit, the force which is created by its twisting often causes wrist injury by the worker's trying to keep it under control. When it is realized that these hole saw-drill combinations are used in areas where it is not easy to see the cutting teeth or how deep they might penetrate, it is not unusual to find that the penetration that results is frequently too great, causing damage to the other components and structure inside the enclosure. As a result, it is very well known that one has to be quite careful in using such a saw--not the least bit of which involves its fairly expensive cost, and which customary usage has shown, results in its being discarded after only several operations.